The present invention relates to a filter employed in laundry washing machines, and more particularly domestic laundry washing machines wherein a laundry load is washed by sprinkling or spraying thereon washing liquid or wash liquor.
As described in European patent application No. 0,202,509, this general type of laundry washing machine essentially includes a wash tub and a laundry receiving basket mounted within the wash tub for rotation therein. A collection chamber or tank is positioned beneath the wash tub and is connected thereto in order to collect wash liquor or washing liquid that is not held back or retained by the laundry within the basket. Such collection tank or chamber is connected both to a discharge or drain duct of the machine via a conventional drain pump and to a sprinkling or spraying assembly located within the top of the wash tub by means of a recirculation duct and a recirculation electric pump. Furthermore, within the collection chamber are located at least one filtering element, an electrical heating element, and a thermostatic sensor for, respectively, filtering, heating and sensing the temperature of the washing liquid.
The filtering element has a fine-meshed surface designed to prevent lint and other impurities transported by the washing liquid from fouling the electric heating element. Thus, such lint and impurities tend to collect on the electrical heating element, thereby lowering its efficiency and reliability over time. This fine-meshed filtering element however has the disadvantage of becoming clogged rapidly and therefore requires that the operator of the machine clean such filter frequently.
To overcome such quick clogging of the filter, it has been proposed, as disclosed in German Patent No. 1,191,781, to provide a laundering filter which is associated with a mechanical device for cleaning the filtering surface of the filter. Such arrangement however is rather complex and expensive.
Additionally, U.S. Pat. No. 3,727,435 discloses a fine-meshed filter for a recirculation-type laundry washing machine which filters the washing liquid which is moved in one direction during recirculation phases toward the washing tub. During the discharge phase, the washing liquid is circulated in an opposite direction, and thereby the material filtered during a previous recirculation phase is carried away from such fine-meshed filter.
Both of these solutions however have the drawback of not providing for removability of the filter and not protecting the drain or discharge pump, particularly if not of the self-cleaning type, from heavy or large size objects (for example buttons, clasps, coins, etc.) which may be carried along by the washing liquid.
It is known in the technology of dish washing machines to provide a fine filtering action in the direction of a recirculation duct and a wide filtering action in a direction toward a drain or discharge duct. Dish washing machines however treat a type of dirt having a form and consistency that are different from that encountered during the washing treatment of laundry. Moreover, between the various elements constituting the filter in a dish washing machine, the fine-meshed component cannot easily be removed and has the function of preventing the obstruction of nozzles of sprinkler arms and not of protecting the surface of electrical heating resistors from foreign objects. Thus, in contradistinction to a dish washing machine, wherein electrical resistor heating elements are located within a tub of the dish washing machine, in a laundry washing machine of the type discussed above, the electrical resistor heating elements are located within the collection chamber and therefore must be protected from foreign objects.